Underground storage system



2 Sheets-Sheet l 1 July 7, 1959 c. T. BRANDT UNDERGROUND STORAGE SYSTEMFiled May 16, 1955 INVENTOR. C.T. BRANDT Byway??? ATTORNEYS July 7, 1959c. T. BRANDT 2,393,211

UNDERGROUND STORAGE SYSTEM Filed May 16, 1955 2 Sheets-Sheet 2 ATTORNEYSUnited States "Patent M UNDERGROUND STORAGE SYSTEM Carl T. Brandt,Bartlesville, kla., assignor to Phillips Petroleum Company, acorporation of Delaware Application May 16, 1955, Serial No. 508,523

12 Claims. (Cl. 61-0.5)

2,893,2ll Patented July 7, 1959 ice cavern, not shown, similar to thecavern 10. Each tunnel should be of sufliciently large cross sectionalarea to per This invention relates to underground storage systems.

The constantly expanding production of liquefied pettroleum gas hascreated a definite problem in providing isu'itable storage facilitiesfor this material. Due to the lfhightvapor pressure of LPG, liquefiedpetroleum gas, para-{ticularly propane, the cost of storage in surfaceequipament, such as steel tanks, becomes excessive due to'the :massive.construction required to withstand thevapor gpressure of the storedmaterial in a safe manner.- This gproblem looms especially large whereit is necessary to :store large quantities 'of' such materials duringthe off- I ing liquid.

: 'pear to be a concrete block, poured so as to fill the cavernentrance, with the necessary piping extending through r'this block intothe cavern. However, such a concrete lblock, even though waterproof,cannot always be degpended upon to be impervious against the pressurizedggases in the cavern. The present invention provides a means of insuringa gas-tight seal in the cavern entrance while still employing a concreteslab or other relatively echeap type of bulkhead.

It is an object of the invention to provide underground :storagefacilities of novelconstruction and arrangement, tsaid facilitiesproviding'storage at a minimum unit cost.

It is a further object to provide such a system in which the cavern isan existing structure such as an abandoned tunnel. l

It is a still further object to provide an-underground storage systemcapable of storing volatile liquids Without .loss.

Figure 1 is a vertical section view, partially inelevation, of theunderground storage system of this invention; and

Figure 2 is an enlarged vertical sectional view of the 1111111161system.

Referring now to the drawings in detail, andparticularly -to Figure l,the underground storage system of this in- "vention includes one or moreunderground storage cav- .erns, one of which is indicated by referencenumeral 10. It will be understood that each cavern can consist of a"large excavated region, as illustrated in Figure 1, or alternatively,the cavern can comprise a series of elongated 1 individual storagechambers of cylindrical or rectangular .cross section with the axis inahorizontal or vertical di- -rection, as desired, all of the chambersdefining the cavern communicating with a common tunnel leading to acentral ;shaft in the manner hereinafter explained.

A tunnel 11 connects the cavern 10 with a shaft 12 exand adjacentchamber.

' ends of which are at the surface of the earth.

mit access thereto by workmen. In one specific embodi ment, the shaft 12is 260 feet deep and extends vertically.

In accordance with the invention, each tunnel ineor porates a sealingstructure, preferably disposed at the end of the tunnel remote from theshaft, to the end that liquid or vapor cannot leak from the caverns intothe tunnels or shafts, even where the stored material is quite volatileand, therefore, develops a high vapor pressure. A suitable sealingstructure is shown in connection with tunnel 11,'this structureincluding a concrete wall or bulkhead 14, preferably formed from pouredconcrete and disposed in the tunnel at the cavern entrance. Between theshaft and bulkhead 14 is a second bulkhead 15, preferably formed frompoured concrete and substantially thicker than the other. In thismanner, a chamber 16 is defined between the bulkheads 14, 15 which canbe filled with a viscous substance, preferably drilling mud, which isimmiscible with the stored product. The means of filling the chamber 16is discussed later in connection with Figure 2. Exterior bulkhead 15 isbuilt to withstand the total pressure exerted by the stored fluid incavern 10. Interior bulkhead 14 is designed only to withstand the smallpressure differential between the stored fluid and the seal- A largetubular conduit or manway 20 extends through bulkheads '14 and 15, oneend extending into and communicating with the cavern 10 and the outerend extending into the tunnel 1 1. v This manway is open on thestorag'eside but the outer end is closed and sealed by a flanged metalcap 21 bolted thereto. Line 22 connects the top of tank 26 with manway20 through cap 21. Line 23 branches from line 22 and connects to the topof tank 25. The bases of tanks 25, 26 are connected through respectivelines 27, 28 to the interior of seal chamber 16. Lines 27, 28 are filledwith the same sealing liquid present in chamber 16; lines '22, 23 arefilled with stored product. The interfaces of the two substances intanks 25, 26 are indicated generally at 30, 31. Pipe 34 provides adirect connection between line 22 and the interior of chamber 16, checkvalve 33 being designed to permit only one-way flow, permitting gasto'enter the seal chamber under conditions described later.

In further accordance with the invention, a filling and dispensing line36 extends through the bulkheads 14, 15

and has one end 37 thereof disposed within the cavern 10.

Preferably, the end 37 is elevated, as by providing supports 38, 38beneath the line, and is slotted on its underside. In this manner,fluids are easily introduced into the line from'the cavern or pass intothe cavern through the line, and there is less chance for the end of thepipe to become clogged by rocks or other debris accumulating at thebottom of the cavern. If desired, additional perforations can beprovided in a portion of the line which rests upon the floor of thecavern to allow removal of residual portions of stored material. Pump 40permits the elevation 'of fluid from line 36 to the surface through line41 extending up through shaft 12 into storage vessel 42.

It is evident that the aforesaid means provides for a substantialequalization of pressure in the storage cavern However, the pressure ofthe drilling mud against bulkhead 14 will always exceed the opposingpressure of the stored product so long as the propane-mud interface inthe equalizer tanks is higher than the top of the sealed chamber.

Figure 2 illustrates in somewhat greater detail the sealing system ofthe invention as applied to a tunnel, both In a typical embodiment,tunnel 10a is an abandoned railroad tunnel in a hill 49, supplied withstorage fluid through line 39,

and closed at each end by bulkheads 14, 14a and 15, 15a

3 of the type described in co nnection with Fi gure 1. The seal spaces16, 16a are filled with a viscous fluid, preferably a drilling mud, asin Figure 1. As shown in the lefthand side of the figure, 'manway20connects through line 22 to tanks25, 26 as in Figure 1 andsafety value.33 is likewisegprovided. V

, A mud recirculating and vent -line50, preferably latwbinch pipe,extends from the top of seal chamber 16 through bulkhead 15 and connectsto the discharge of mud 'pump :52. A similar pipe ,53 extends from thebase of seal chamber 16 through bulkheadf1f5 to the pump 52 and to tank26 forming an interface between the stored fluid and the sealing fluidat the levelindicated. Line .54 branches from line 53 connects to the bas efof tank 25 forming a similar interfacetherein. Thelope ration ofpump 52 maintains circulation of the mud from seal chamber 16 to thepump and back.

When mud is first pumped into chamber 1 6 it is -admitted from pump 56to line 53 on opening valve :58. 'It is thus pumped through line 53 intothe base or chamber 16. Air displaced from chamber'16 is ve nt'edthrough line 50 by opening valve 61. Once chamber 16 is filled, valves58 and 61 are closed and valve 60 opened. Pump 52 now draws mud throughline 53 and returns it through line 50. When mud needs to be added tothe system during normal storage, it is admitted throughline 57 byopening valve 58 and operating pump 56. It should be understood that theseal system at the other end of the tunnel, indicated generally by pipesextending through bulkheads 14a, 15a, is identical with that justdescribed and, hence, need not be described further. 7 V V V Conduits22, 23 are connected to blowdown lines 62, 63, respectively, which arevalved at 64, 65, respectively. Conduits 22,23 are valved at 67, 68below the blowdown line connections. This provides a simple means forrelieving the gaspressure in the upper portions of lines 22, 23. Forexample, tank 26 can be, in eifeca disconnected from the system byclosing valves 67, 70 and then opening valves 64, with a resultantescape of gas pressure in the upper part of line 22. Tank 25 can bedisconnected in a similar manner by closing valves 68, 71 and openingvalve 65. 7

Interior bulkhead 14in Figures 1 and 2 is designed to Withstand a smalldifferential pressure only. The function of line 34 is to protect theinterior bulkhead from rupturing due to excess differential pressure ifthe mud seal is lost. Normally the equalizer tanks take care of this butif the mud lines become plugged and pressure cannot be maintained on theseal because of slight leakage, it is evident that a pressuredifferential between stored gas and the drilling mud seal'would quicklyform. That is, if the gas pressure is unable to force mud down from theequalizer tankvand mud waslbeing losuthe pressurein the seal would dropbelow the pressure in the cavern. This invites a possible break-throughof stored LPG. To avert this, valve 33 in line 34 will open when the gaspressure in the cavern exceeds the pressure in the seal chamber. Enough\gas then flows through the valved lines into the seal chamber tobalance the pressure on each side of the valve and, hence, on each sideof the inner bulkhead 14. In this way line 34 serves as a safetyfeature.

The mud used in chamber 16should be viscous but fairly fluid and shouldbe a low water-losstype. A preferred composition is a bentonite-sodiumcarboxyrnethyl cellulose-water mixture having 6.8% by Weight ofbentonite (22 pounds/bbl.) and 1-3 pounds of sodium carboxymethylcellulose/bbl. of total mud.

To illustrate the operation of the system assume that the product storedis propane '(sp. gr..=.5 1), exerting a pressure of 150 p.s.i., and theheavy media fluid' is 8.7# drilling mud with asp'ecific gravity0151.045. Assume the bulkheaded opening is 20 feet high and that thecontactof propane andmud is 8" fee-tabove theltopbf the scheme,I'provide the aforementioned direct connection tunnel (Figure 2). If 150p.s.i. is exerted by the propane at the top of the tunnel 10a, thepressure transferred through the top of the column 23 to the propane-mudinterface will be reduced by about 1.8 p.s.i.

and hence will be about 148.2 at this point. 'This pres sure will betransferred to the mud and will be increased by the weight of the muddownward in the column. Thus, at -8 feet down from the contact and atthe top of the opening, the pressure will increase 'by 3.6 p.s.i. andwill be 151.8 p.s.i. At 28 feet down from the contact and at the bottomof the bulkheaded opening, the pressure will increaseby 12.7 psi. andwill be 160.9 p.s.i. These pressureswill be transferred to similarlocations within the :seal chamber. Thus, at the top of the intermediatebulkhead 14 a'pressure of 151.8 p.s.i. is exerted by the mud as against150'p.'s.-i. of the propane; at the bottom ofthe bulkheadfthepressure-of the mud will be 160.9 p.s.i. against 'the 154 p.s.i. exertedby the propane. Hence, the 'mud in chamber 16 tends to flow through :the"bul-khead'into the tunnel. However, since it is too viscousto flowthrough theinterstices, there will be no flow and a'--sta-tic conditionwill exist which will efiFectively-seal the bulkhead. I '-It;-will-=beevident that the heavier the mud the greater the pressuredifferent-ia'lacross bulkhead 14. When the stored product is volatile,e.g. LPG, it is preferred to provide heaters, suchas electric heatingelements 75, 76, bnthe ldwer'portionof lines-.22and 23. Inthis wayEa'coIumn of vapor can be maintained in these lines, thus increasing thepressure differential between chamber 16 andthe interior of the cavern.

'The pressure exerted by the heavy mediaitself is con- .stantand is-onlysupplemented by the pressure exerted by the-propane. 'Thus, the 'totalpressure exerted on the heavy'media'within-thesealchamber-will always bein excess of the pressure of the propane. For example,

using the values just illustratedthe pressure differential between themud andpropane at the top of thebulkhead {1.8 pounds) 'would be the-samewhether the pressure of the propane against the top ofthe bulkhead rosefrom .150 p.s.i. up [0200 p.s.i. orfell to p.s.i. Similarly the pressurediiferential at the base of thebulkhead would 'r'emain'constantat 6.9pounds. Therefore, the

However,-as an added precaution against the rupturing of theintermediate bulkhead by a pressure diflferential build-up due to some-malfunction of the between the propane side and the seal chamberfalongwith'its" check valve 33. Flow of propane into the void in'thesealchamber' will thus equalize the pressures at any time when the mudexerts insufiicient pressure to keep the check valve closed.

It is evident that other heavy media than mud having suitable'viscositvand weight could be used in the seal atother points in thesystem without departing from the basic invention.

I claim: 1: In an'underground storage system, in combination,

'an' underground storagecavern, a tunnel connected to "said cavern, apair of'spaced fluid-tight barriers in said tunnel forming a sealchamber therein, a volatile liquid stored Within'said cavern underpressure, a viscous liquid immiscible with and having a greater specificgravity than the stored liquid occupying the chamber between the twobarriers, said latter viscous liquid exerting a pressure *against-theinner barrier which is greater than the opposing pressurethe'reon so asto preventleakage through the tunnel from the cavern, meansforadrnitting and withdrawing liquid from both the cavernand thechamber, and pressure controlling means comprising a conduit having oneend connected with the interior of the cavern and the other endconnected with the interior of the seal chamber and an intermediateportion thereof positioned above the level of the barriers and externalthereto, whereby the two liquids form an interface within saidintermediate portion of the conduit, the liquid above the interfacebeing the stored fluid, thereby effecting a small pressure differentialbetween the two liquids.

2. Apparatus of claim 1 wherein the interface is maintained above thelevel of the barriers, the weight of the intervening head of liquidproviding the pressure differential between the cavern and the sealchamber.

3. In an underground storage system, in combination, an undergroundstorage tunnel, a pair of spaced substantially water-tight concretebulkheads in said tunnel, each sealing the tunnel from fluid flowtherethrough, a volatile liquid storage within said tunnel underpressure, a viscous liquid immiscible with and having a greater specificgravity than the stored liquid occupying the chamber between the twobulkheads, said liquid exerting a pressure greater than that of thestored liquid and forming a liquid seal to prevent escape of storedproduct through the bulkhead, means for circulating the viscous liquidto maintain its density uniform, a tank positioned with its upper endabove the upper level of the tunnel, a conduit extending from within thetunnel through said bulkheads to the top of said tank, said conduitbeing filled with stored fluid, and a second conduit extending from thebase of the tank into the lower portion of said chamber and filled withsaid viscous liquid, the interface of the two fluids being within saidtank, whereby the Weight of the head of seal liquid between theinterface and the top level of the tunnel is suflicient to maintain apressure against the inner bulkhead in excess of the opposing pressureof the stored liquid.

4. The system of claim 3 wherein the means for circulating the sealliquid comprises a pump having a line extending into the upper portionof the seal chamber and a second line extending into the lower portionof the seal chamber, the operation of said pump serving to draw liquidfrom the lower portion of the chamber and to discharge it into the upperportion of the chamber. A 5. Apparatus of claim 4 wherein the secondline comprises means for introducing liquid thereto from an externalsource.

6. In the system of claim 3, a safety device to prevent possible failureof the inner bulkhead, said device comprising a line establishingcommunication between the stored liquid and the interior of the sealchamber, said line being provided with a valve which opens only topermit admission of stored liquid into said chamber, thereby permittingstored liquid to enter the seal chamber to equalize the pressure acrossthe valve whenever the seal liquid exerts insufficient pressure to keepthe valve closed.

7. In an underground storage system, in combination, an undergroundtunnel, a pair of spaced fluid-tight barriers in said tunnel arranged toseal same against fluid flow therethrough, a stored liquid contained onone side of said barriers, a seal liquid immiscible with the storedliquid occupying the space between the barriers, said seal liquidexerting a pressure against the inner barrier which is greater than theopposing pressure thereon so as to prevent leakage of stored liquidthrough the tunnel, and means for maintaining this pressure differentialacross the inner barrier which comprises a colunm of fluid having agreater specific gravity than the stored liquid, said column extendingfrom the bottom of the space between said barriers to a point above thisspace thereby applying the head pressure of said column to said sealliquid, and conduit means supplying pressure communication from saidstored liquid to the top of said column thereby applying pressure to thetop of said column at least equal to the pressure at a point 0fcorresponding level within said stored liquid.

8. In the system of claim 7, means for heating stored liquid into vaporin said conduit means thereby providing a vaporous medium to supply saidpressure communi cation to the top of said column.

9. In the system of claim 7, a safety device to prevent possible failureof the inner barrier, said device comprising a line establishingcommunication between said stored liquid and the space between saidbarriers, said line being provided with a valve which opens only topermit admission of stored liquid into the space between said barriers,thereby permitting stored liquid to enter the space between saidbarriers to equalize the pressure across the valve whenever said sealliquid exerts insutficient pressure to keep the valve closed.

10. In an underground storage system the apparatus of claim 7, whereinthe stored liquid is LPG and the seal liquid and fluid having a greaterspecific gravity than the stored liquid are a viscous fluid drillingmud.

11. In an underground storage system, in combination, an undergroundtunnel, a pair of spaced substantially water-tight bulkheads in saidtunnel, each bulkhead sealing the tunnel from fluid flow therethrough, avolatile liquid contained on one side of said bulkheads, a seal liquidimmiscible with and having a greater specific gravity than said volatileliquid occupying the space between the two bulkheads, said seal liquidexerting a pressure greater than that of said volatile liquid andforming a liquid seal to prevent escape of said volatile liquid throughthe bulkheads, a chamber positioned with its upper end above the upperlevel of the space between the bulkheads, a conduit extending from thevolatile liquid contained by said bulkheads to the top of said chamber,said conduit being filled with said volatile liquid, and a secondconduit extending from the base of said chamber into the space betweensaid bulkheads and filled with said seal liquid, the interface of thetwo liquids being within said chamber, whereby the weight of the head ofseal liquid between the interface and the top level of the space betweenthe bulkheads is sufficient to maintain a pressure against the innerbulkhead in excess of the opposing pressure of the contained volatileliquid.

12. In an underground storage system, in combination, an undergroundstorage cavern, a shaft extending from the surface of the earth to apoint adjacent said cavern, a tunnel connecting said shaft with the baseof said cavern, a pair of spaced fluid-tight barriers in said tunnelforming a seal chamber therein, a volatile liquid stored within saidcavern under pressure, a viscous liquid immiscible with and having agreater specific gravity than the stored liquid occupying the chamberbetween the two barriers, said latter viscous liquid exerting a pressureagainst the inner barrier which is greater than the opposing pressurethereon so as to prevent leakage through the tunnel from the cavern,means for admitting and withdrawing liquid from the cavern, and pressurecontrolling means comprising a conduit having one end connected with theinterior of the cavern and the other end connected with the interior ofthe seal chamber and an intermediate portion thereof positioned abovethe level of the barriers and external thereto, whereby the two liquidsform an interface within said intermediate portion of the conduit, theliquid above the interface being the stored fluid, thereby effecting asmall pressure dilferential between the two liquids.

References Cited in the file of this patent UNITED STATES PATENTS2,459,227 Kerr Jan. 18, 1949 2,508,949 Howard May 23, 1950 2,659,209Phelps Nov. 17, 1953 OTHER REFERENCES Volclay pamphlet 2 29, copyright1936 by the American Colloid Co.

